Higher Layer Half Duplex HARQ Management for Energy Harvesting Devices
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Solution Overview
Problem
In 5G wireless systems, energy harvesting devices (EHDs) with limited power storage and processing capabilities face challenges in efficiently managing hybrid automatic repeat request (HARQ) processes, leading to excessive energy consumption and potential radio link failures due to simultaneous downlink and uplink transmissions, which are not effectively coordinated between Layer 1 and Layer 2.
Innovation Solution
Implementing a higher layer half-duplex frequency division duplex (HD-FDD) operation mode that dynamically configures HARQ processes based on energy levels, allowing for reduced PDCCH monitoring and buffering of Layer 2 packets, thereby optimizing energy use and avoiding simultaneous downlink and uplink transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If energy harvesting devices perform simultaneous downlink and uplink transmissions with full HARQ processes, then communication reliability is improved, but energy consumption increases excessively
Solution Approach 1:
The patent implements dynamic HARQ process management where the number of active HARQ processes is adjusted based on device energy levels. When energy is abundant, more HARQ processes can be maintained for reliable communication. When energy is low, the system reduces the number of active HARQ processes to conserve energy, creating a dynamic adaptation between communication reliability and energy consumption.
Solution Approach 2:
The system changes the parameter of HARQ process count based on energy conditions. By modifying this key parameter, the system can transition between different operational modes - maintaining full HARQ processes for high reliability when energy permits, or reducing to minimal processes for energy conservation when needed, thus resolving the contradiction between reliability and energy use.
2Reliability
If energy harvesting devices monitor all downlink control information continuously, then transmission reliability is improved, but energy depletion occurs faster
Solution Approach 1:
Instead of continuous DCI monitoring, the system implements periodic monitoring where the device monitors downlink control information at specific intervals or only when necessary. This periodic approach maintains adequate transmission reliability by catching important control signals while significantly reducing the energy consumption associated with continuous monitoring, thereby extending operational duration.
Solution Approach 2:
The system performs partial DCI monitoring rather than complete continuous monitoring. By monitoring only a subset of control information or monitoring at reduced frequency, the system achieves sufficient transmission reliability for critical operations while conserving energy to extend the device's operational lifetime.
3Reliability
If energy harvesting devices increase HARQ process buffer size, then data transfer completeness is improved, but energy storage requirements increase
Solution Approach 1:
The HARQ buffer size is made dynamic rather than fixed. The system adjusts the buffer size according to available energy storage capacity and current communication requirements. When energy storage is abundant, larger buffers can be allocated to ensure complete data transfer. When energy storage is limited, the buffer size is reduced to fit available resources, thus resolving the contradiction between data completeness and storage requirements.
Solution Approach 2:
The system changes the buffer size parameter based on energy conditions. By dynamically adjusting this parameter, the system can optimize the trade-off between maintaining sufficient buffer capacity for complete data transfer and adapting to limited energy storage resources available in energy harvesting devices.
4Productivity
If energy harvesting devices operate in full duplex mode, then spectral efficiency is improved, but coordination between Layer 1 and Layer 2 becomes complex
Solution Approach 1:
The patent segments the HARQ management functionality into distinct layers with clear interfaces. Layer 1 handles physical layer transmissions while Layer 2 manages HARQ process coordination, with well-defined boundaries and interaction protocols. This segmentation reduces the coordination complexity by preventing overlapping responsibilities and conflicts between layers, while still enabling full duplex operation for spectral efficiency.
Solution Approach 2:
The patent introduces an intermediary HARQ management layer that mediates between Layer 1 and Layer 2 operations. This intermediary component coordinates the interactions, manages the HARQ processes, and resolves potential conflicts between simultaneous downlink and uplink transmissions, thereby reducing overall system complexity while maintaining full duplex spectral efficiency.
Data Source
AI summary
A method for higher layer half duplex operation is provided. The method for higher layer half duplex operation may include receiving, from a serving cell, a configuration for a maximum number of downlink and/or uplink hybrid automatic repeat request processes. The method may also include providing an indication to the serving cell that includes a desired maximum number of uplink hybrid automatic repeat request processes based on an energy level of an apparatus and performing downlink control information monitoring for downlink or uplink until the maximum number of hybrid automatic repeat request processes is reached. The downlink control information monitoring may be suspended when a corresponding maximum number of downlink or uplink hybrid automatic repeat request processes is exceeded.